It's worth it.. Just turn off the vsync.
You can only see a maximum of 60 fps on a 60Hz moniter.... with or without v sync.
If you have the cash OP then SLI GTX 570 is definitely worth it. Its cheaper and more powerful than a GTX 590.
Although there is no such thing as future proof with computers, SLI GTX 570 is about as close as your going to get at the moment and you will more then likely be able to max games for the next 1-2 years.
You will not be able to max BF3 and get 60 fps with a single GTX 570 but you will max it with GTX 570 SLI with at least 60 fps.
You may find this interesting, http://uk.geforce.com/optimise/guides/battlefield-3-beta-performance-guide
bare in mind that the GTX 570 gets just under 60 fps on "High" settings not "Ultra". With GTX 570 SLI you should get around 80 fps on "Ultra". I say this because GTX 560 SLI gets 80 fps on "High" so GTX 570 SLI should get 80 fps on "Ultra".